| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain a two-frequency communication system in RFID communication, which can automatically recognize two carrier frequencies to switch and use the frequencies, and establishes compatibility between a plurality of carrier frequencies. <P>SOLUTION: In a front end of an RFID chip, two sets of antenna tuning circuits, i.e. an antenna tuning circuit for 950 MHz and an antenna tuning circuit for 13.56 MHz are connected, a detection rectification circuit for envelope detection and power supply, a voltage detecting circuit and a frequency dividing circuit for dividing a frequency to value of near 13.56 MHz are provided on the poststage of the antenna tuning circuit for 950 MHz, and a detection rectification circuit for envelope detection and power supply and a voltage detecting circuit are provided on the poststage of the antenna tuning circuit for 13.56 MHz. Moreover, a clock generating circuit for generating a system clock, a modulating circuit for applying load modulation to each of the antenna tuning circuits, and a switching element and the like are provided to constitute the apparatus. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
